Caribachlamys jungi Waller, 2011
WALLER, T. R. 2011. Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley. Bulletins of American Paleontology, 381: 1-197, pls. 1-18. [p. 28, pl. 2, figs. 1-5]
2011 Caribachlamys jungi Waller, 2011
T. R. Waller, 2011, plate 2.
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«Description.— Shell small, not known to exceed 15 mm Ht, height exceeding length in ratio of 1.12:1, umbonal angle moderately narrow, ca. 95°, prosocline, of moderate convexity with LV slightly more convex than RV, lacking disk gapes. Disks with numerous closely spaced radial costae varying in width and not clustered; costae beginning at 0.9 mm from beak, initially 11 or 12 in number, then increasing rapidly to 35-40 at 5 mm Ht and ca. 60 by 10 mm Ht; mode of increase initially by intercalation on both valves, later by intercalation throughout ontogeny of LV and initially by intercalation and later by branching on RV; costae rounded, bearing small distally concave scales that are more strongly developed at sides of disk than in central part; interspaces bearing strong antimarginal microsculpture, most strongly developed at sides of disk and on disk flanks; regular commarginal lamellae absent; disk flanks costate, with costae merging with those of auricles on left anterior and both posterior sides. Auricles very unequal, anterior outer ligament groove twice the length of posterior outer ligament groove; right anterior auricle with 7 radial costae crossed by imbricated commarginal lamellae, bordered ventrally by broad, commarginally rugose byssal fasciole; byssal notch deep with rounded apex, floored by active ctenolium having 3 or 4 strong teeth, anterior margin broadly rounded; left anterior auricle with sigmoidal margin and shallow byssal sinus, overall trend of margin forming acute angle with dorsal margin, bearing 15-17 closely spaced, scabrous radial costae that transition to costae of anterior disk flank; posterior auricles with 5 or 7 somewhat weaker scabrous costellae, posterior margins of posterior auricles slightly outwardly convex to nearly straight, forming obtuse angle with dorsal margin. Hinge dentition as in Chlamys, with strong dorsal and resilial teeth on RV and corresponding sockets on LV. Ribs on interior of shell lacking carinate edges near shell margin. Adductor scars not well preserved and shapes not determined. Foliated-calcite re-entry lacking, umbonal areas of disk interiors entirely aragonitic. Prodissoconchs not preserved.
Etymology.— Named in honor of Dr. Peter Jung of Basel, Switzerland, one of the founders of the Dominican Republic Project, who patiently sorted tens of thousands of macrofossils and entrusted the study of selected groups to taxonomic specialists. Type material.— Holotype, NMB G17495, 1 LV, 14.5 mm Ht, 13.0 mm L (Pl. 2, Figs 1-2). Type locality.— NMB 16934 (= NMB 15855), left bank of Río Gurabo ca. 1.5 km upstream from crossing of the old road running from Sabaneta to Los Quemados, lower Gurabo Formation, ca. 274-277 m above base of section (Saunders et al., 1986: 62, text-fig. 4), Upper Miocene. Other material.— Paratype (Pl. 2, Figs 3-5), 1 RV, USNM 540948, from locality TU 1215 (= USGS 8539-8543), "Río Gurabo, bluffs on both sides, from the ford on the Los Quemados-Sabaneta road upstream to approximately 1 km above the ford (= USGS 8539-8543; Maury's Zone D)" (Saunders et al., 1986: 64). Text-fig. 4 of Saunders et al. (1986) indicates that this site ranges from ca. 275-384 m above the base of the section, in the Upper Miocene part of the Gurabo Formation. Remarks.— The two specimens of Caribachlamys jungi n. sp. are almost the same size and have anterior and posterior hinge lines of identical length, suggesting that they could be matching valves, even though one was collected by the NMB team and the other by the Vokeses. This, however, is not the case in that growth disturbances on the right valve are not refl ected on the left valve. As with C. guayubinensis n. sp., the prodissoconchs of C. jungi n. sp. are not preserved, and placement in the genus Caribachlamys is based on rib pattern, scale development, and microsculpture. At the type locality (NMB 16934 = NMB 15855), the only pectinid found in association with Caribachlamys jungi n. sp. is Nodipecten colinensis vokesae. At the other locality (TU 1215), there is a much richer assemblage of associated pectinids (Argopecten thetidis, Lindapecten paramuscosus, Antillipecten quemadosensis n. sp., and Amusium papyraceum Morphotype C), possibly refl ecting the greater spatial and stratigraphic span of this locality. Saunders et al. (1986: 54) commented that at NMB 15855, the fossils are "scattered in silts and coral rubble around huge, partly inverted coral heads." For locality TU 1215, E. Vokes (1989: 16) referred to the outcrop as consisting of "alternating layers of branching coral masses and green shale" rich in muricid gastropods. She interpreted this as a coralline facies of the Gurabo Formation representing depths of 20-50 m. The associated pectinids suggest the deeper end of this range or deeper, with the corals having been tumbled downslope into fi ne sediments. Comparisons.— Among the known species of Caribachlamys (Waller, 1993), C. jungi n. sp. is closest to the Recent species C. sentis (Reeve, 1853) of the tropical and subtropical western Atlantic, Gulf of Mexico, and Caribbean (Waller, 1993: 217). Caribachlamys sentis of comparable size to the new species differs in having a narrower umbonal angle that is < 90º, fewer and stronger radial costae with larger scales that extend across the rib crests, and a relatively larger left anterior auricle with a straighter anterior margin that forms a sharper angle with the dorsal margin. Caribachlamys paucirama Waller, 1993, from the Middle and Upper Pliocene and Lower Pleistocene of Florida, resembles C. jungi n. sp. in the shape of its left anterior auricle, but differs in having an umbonal angle of < 90º, fewer costae that are separated near the margin by interspaces as wide or wider than the costae, and relatively broader scales that extend across the rib crests. Caribachlamys jungi n. sp. superficially resembles species in the genus Spathochlamys Waller, 1993, but unlike that genus, its scales are concave in the direction of shell growth, rib interspaces lack commarginal lirae, there are no regular medial costellae, and the edges of ribs on the inner surface near the margin lack carinate edges. Evolution.— Waller (1993) reviewed the fossil record of Caribachlamys, which at that writing extended only as far back as the Pliocene. Caribachlamys jungi n. sp., from the Upper Miocene part of the Gurabo Formation, is therefore the oldest known species in the genus. It might have given rise to C. sentis, the stem species of the genus as depicted in the phylogeny of Waller (1993: fi g. 8). Occurrence and distribution.— Known only from the lower part of the Gurabo Formation, of Late Miocene age, on the Río Gurabo, northern Dominican Republic.» THOMAS RICHARD WALLER, 2011
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